OBJECTIVETo observe the changes in the expression of connective tissue growth factor (CTGF), type I collagen (Col I), and type III collagen (Col III) among the rats with acute paraquat (PQ) poisoning and the intervention effect of pyrrolidine dithiocarbamate (PDTC) on their expression, and to investigate the mechanism of PQ-induced pulmonary fibrosis and the intervention effect of PDTC on the disease.

METHODSSprague-Dawley rats were randomly divided into control group (n = 6), PQ group (n = 36), and PQ + PDTC group (n = 36). The PQ group and PQ + PDTC group were given a single dose of saline-diluted PQ (80 mg/kg) by gavage; 2 h later, the PQ + PDTC group was intraperitoneally injected with a single dose of PDTC (100 mg/kg), and the PQ group was intraperitoneally injected with the same amount of saline. The control group was given saline (1 ml/kg) by gavage and was intraperitoneally injected with the same amount of saline 2h later. At 1, 3, 7, 14, 25, and 56 days after operation, the protein expression of CTGF was evaluated by Western blot; the mRNA expression of CTGF, Col I, and Col III was analyzed by real-time quantitative PCR; the content of hydroxyproline in lung tissue was measured, and the pathological changes of lung tissue of the poisoned rats were observed.

RESULTSThe protein expression of CTGF in the PQ group increased as the time went on, slowly from the 3rd to the 14th day and rapidly from the 28th to the 56th day, significantly higher than that in the control group at each time point (P < 0.05 or P < 0.01). The mRNA expression of CTGF in the PQ group began to rise markedly on the 1st day, increased rapidly from the 3rd to the 14th day, and remained at a relatively high level from the 28th to the 56th day, significantly higher than that in the control group at each time point (P < 0.01). The mRNA expression of Col I in the PQ group changed little on the 1st and 3rd day, increased slightly on the 7th day, and increased greatly from the 14th to the 56th day, significantly higher than that in the control group from the 7th to the 56th day (P < 0.05 or P < 0.01). The mRNA expression of Col III in the PQ group began to rise on the 1st day, reached the peak level on the 7th day, and then declined, significantly higher than that in the control group at each time point (P < 0.05 or P < 0.01). Masson staining showed that fibroblasts proliferated from the 14th to the 28th day, and collagen fibers increased gradually. Compared with the PQ group, the PQ + PDTC group showed significantly decreased protein expression of CTGF as well as mRNA expression of CTGF, Col I, and Col III (P < 0.05 or P < 0.01).

CONCLUSIONIn PQ-induced pulmonary fibrosis, the expression of CTGF keeps rising, and the collagen secretion and matrix synthesis are increased probably by upregulating the transcriptional levels of Col I and Col III; CTGF plays an important role in PQ-induced pulmonary fibrosis. PDTC can inhibit the expression of CTGF, thus reducing the lung injury in rats with PQ poisoning.